An in-depth investigation of the energy distribution of doubly charged ions emitted from a liquid metal alloy ion source

We investigate the energy spread, DeltaE(1/2), versus emission current, i, of the doubly charged ions emitted by a Au77Ge14Si9 liquid metal alloy ion source. For the ionic species of main interest, namely Ge2+, two modes were found with regard to the dependence of DeltaE(1/2) on i. In the first mode DeltaE(1/2) proportional to i(0.3), and in the second DeltaE(1/2) proportional to i. The difference is attributed to changes in the composition of the alloy during field evaporation. Au2+ and Si2+ were also found to obey a DeltaE(1/2) proportional to i(0.3) law; in the case of Si2+ however, there is a deviation from this law at high currents.